The Gliointerstitial System of Molluscs

Nicaise, Ghislain

doi:10.1016/s0074-7696(08)61938-5

Cited by 69 publications

(19 citation statements)

References 208 publications

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“…14) (Norenburg, 1982;Turbeville and Ruppert, 1983) whereas in others the granules are predominately below the dermis. Some of these cells appear to be associated with the nervous system and similarity to the gliointerstitial systems described by Nicaise (1973) and Rieger (19816) seems evident (see also Turbeville and Ruppert, 1985). The hoplonemertines examined, with the exception of Carcinonemertes epialti, have a more or less conspicuous zone of vacuolate-appearing, cup-like structures between the epidermis and the basal lamina (Figs.…”

Section: General Structurementioning

confidence: 59%

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Norenburg

1985

Am Zool

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SVNOPSIS. The phylum Nemertina, with more than 800 described species, occupies a wide range of habitats and figures prominently in theories of bilaterian evolution. Integuments of nemertines, from a number of habitats and representing the major orders, are compared and the general cell types constituting the epidermis are reviewed and defined. The general construction and cell demography of the integument are more or less characteristic for each order, but are not readily generalized to lower taxonomic levels. Similarly, the general structure of the integument has correlations with broad environments, but there are few conspicuous, uniquely adaptive, morphological specializations; e.g., the adhesive plate and ciliary bristles of interstitial nemertines, the tube-forming cells of Carcinonemertes epialti and various palaeonemertines, the epidermis of the pilidium larva. It is proposed that there are three generalized types of integumentary glandular cells, mucous, serous and bacillary, and that these and the ciliated cells vary only modestly across taxonomic and environmental lines. However, it is also proposed that the major structural variations of the integument not only are diagnostic for the orders but also suggest and correlate with two major evolutionary radiations of the extant nemertines, one epibenthic, the other infaunal-in that sequence. Similarities of the nemertine integument to that of turbellarians are superficial or at best plesiomorphous; i.e., they are also found in other taxa.

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Section: General Structurementioning

confidence: 59%

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Norenburg

1985

Am Zool

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“…The whole-cell experiments yielded little relevant information, for two main reasons. First, perineuronal satellite cells in invertebrates form a series of cytoplasmic layers around the nerve cell and are interconnected by electrical junctions (Nicaise, 1973). The input resistance measured in the whole-cell recording mode therefore resulted mainly from currents spreading over the glial layer.…”

Section: Discussionmentioning

confidence: 99%

Glial potassium channels activated by neuronal firing or intracellular cyclic AMP in Helix.

Gommerat¹,

Gola²

1996

The Journal of Physiology

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1. Cell-attached and whole-cell patch clamp experiments were performed on satellite glial cells adhering to the cell body of neurones in situ within the nervous system of the snail Helix pomatia. The underlying neurone was under current-or voltage-clamp control. 2. Neuronal firing induced a delayed (20-30 s) persistent (3-4 min) increase in the opening probability of glial K+ channels. The channels were also activated by perfusing the ganglion with a depolarizing high-K+ saline, except when the underlying neurone was prevented from depolarizing under voltage-clamp conditions. 3. Two K+-selective channels were detected in the glial membrane. The channel responding to neuronal firing was present in 95% of the patches (n = 393 During the last decade, a corpus of data has accumulated demonstrating that glial cells possess a wide range of ion channels (reviews by Barres, Chun & Corey, 1990;Barres, 1991;Chiu, 1991;Ritchie, 1992;Sontheimer, 1992) and neurotransmitter receptors (Barres, 1991). This prompted the idea that messages might be exchanged between glial cells and neurones. Most of these data, however, were collected in vitro in glial cell cultures or acutely dissociated glial cells, and comparatively little is known about how these cells communicate in situ. This raises the question as to whether channel and receptor expression may be epiphenomenal to cell culture. Several attempts have therefore been made to record the activity of glial cells in intact

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“…The change in the number of glial granules had been predicted by the hypothesis of a granular calcium store, allowing glial cells to regulate the perineuronal calcium concentration (Gambetti et al, 1975;Nicaise, 1973). The possibility that glia could adjust the ionic composition of the perineuronal spaces has prompted many studies on potassium glial regulation (Abbott et al, 1988;Orkand, 1977;Pentreath, 1982;Walz and Hertz, 1983), a few on sodium (Treherne and Schofield, 1981; …”

Section: Discussionmentioning

confidence: 99%

“…Even with as much as 10 mM Ca2+ in the milieu, a calcium store may counter the antagonistic effect of Na' on Ca2+ fluxes that has been observed in several physiological mechanisms: the [Ca2+]JNat]E ratio was shown to be critical in cardiac muscle contraction (Luttgau and Niedergerke, 19581, in smooth muscle spike amplitude (Connor and Prosser, 1974), and in neurotransmitter secretion (Blaszkowski and Bogdanski, 1971;Dreifuss et al, 1971). The hypothesis that calcium-containing membrane-bound glial granules could function as a Ca2+ store to regulate the perineuronal spaces has been proposed for molluscs (Nicaise, 1973) and also vertebrates (Gambetti et al, 19751, with little experimental evidence in either case. It has been noted that marine invertebrates often have more glial granules than freshwater species of the same phyla (Hemming and Nicaise, 1982).…”

Section: Introductionmentioning

confidence: 99%

The abundance of Aplysia gliagrana depends on Ca²⁺ and/or Na⁺ concentrations in sea water

Keicher¹,

Maggio²,

Hernandez‐Nicaise³

et al. 1992

Glia

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The glial cells surrounding the identified giant nerve cell bodies R2 or LP1 of Aplysia punctata were studied by quantitative electron microscopy. They contain specific, electron-dense but non-osmiophilic membrane-bound granules, approximately 0.3 microns in diameter, called gliagrana. Similar glial granules are more often found in marine than in freshwater molluscs, possibly because they represent a calcium store used to compensate excess Na+ in the extracellular milieu of marine species and to regulate perineuronal calcium concentration. In agreement with this hypothesis, the abundance of gliagrana (= number of glial granules per microns 2) is found to be higher in animals adapted to low Ca2+ artificial sea water than in animals kept in high Ca2+ (or low Na+) conditions. This finding is not observed after 1 week but after 2 weeks of adaptation.

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The Gliointerstitial System of Molluscs

Cited by 69 publications

References 208 publications

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Glial potassium channels activated by neuronal firing or intracellular cyclic AMP in Helix.

The abundance of Aplysia gliagrana depends on Ca²⁺ and/or Na⁺ concentrations in sea water

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The Gliointerstitial System of Molluscs

Cited by 69 publications

References 208 publications

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

Glial potassium channels activated by neuronal firing or intracellular cyclic AMP in Helix.

The abundance of Aplysia gliagrana depends on Ca2+ and/or Na+ concentrations in sea water

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The abundance of Aplysia gliagrana depends on Ca²⁺ and/or Na⁺ concentrations in sea water